爱玺玺

package app;

import java.util.Calendar;

public class Test {

 public static void main(String[] args) {
  System.out.println(getMaxDays(2021, 1));
  
  Calendar calendar = Calendar.getInstance();
  System.out.println(calendar.get(Calendar.DATE));
 }
 public static int getMaxDays(int year,int month) {
  //获取本月天数
  Calendar calendar = Calendar.getInstance();
  calendar.set(Calendar.YEAR, year);
  calendar.set(Calendar.MONTH, month-1);//国外月份从0开始计数
  calendar.set(Calendar.DATE, 1);
  calendar.roll(Calendar.DATE, -1);//日期返回一天，就是上月最大天数
  int maxDays = calendar.get(Calendar.DATE);//获取当前日期天数
  return maxDays;
 }

}